This invention is directed to toner and developer compositions, and more specifically to toner compositions having incorporated therein release additives. Accordingly, in one embodiment of the present invention there are provided toner compositions comprised of certain polymers having incorporated therein release additives inclusive of silicone oils. Thus, for example, the toner compositions of the present invention are comprised of polymers, especially polyesters, containing polydialkyl siloxane units with hydroxy termination groups incorporated into the backbone of the polymer resin; and wherein the resin includes therein a release agent. The resulting toners can be selected for electrostatographic, especially xerographic, printing and imaging systems wherein release agent management devices for containing, directing and metering the release additive to the fixing roller are eliminated. Thus, the toner and developer compositions of the present invention are particularly useful in effecting the fusing of images with fuser systems wherein offset preventing devices for retaining and directing release fluids, such as silicone oils, is avoided. Advantages of the aforementioned composition permit a significant reduction in the cost of fusers by removal of offset preventing oil delivery hardware, consequent reduction in the cross sectional size of the fuser, reduced contaminants and dirt in the copying machine, and easier user maintenance. Additional benefits provided with the compositions of the present invention, particularly with known silicone elastomer fuser roll coatings, are enhanced roll stability (life) when a Release Agent Management (RAM) system is not employed. Also, with the toner compositions of the present invention, the release additives are controllably retained in the polymers selected, thereby avoiding undesirable leaching therefrom. Also, elimination of the release agent management system prevents the problem of not being able to write or type on a copy, which has been associated with large amounts of deposited oil. Further, with the toners containing the polyester polymers illustrated herein the release component, such as a silicone oil, is contained within the toner because of its compatibility with the siloxane backbone until its release by heat and pressure in the fuser nip present in electrophotographic systems. Simple oil addition to toners typically causes poor flow and a wet feel due to oil incompatibility with the toner resins. In addition, the toner compositions of the present invention can contain in various effective amounts other components including, for example, charge enhancing additives, carbon black, magnetite, color pigments or dyes; additives such as colloidal silicas, chemically modified colloidal silicas, metal salts, metal salts of fatty acids, reference U.S. Pat. No. 3,590,000, the disclosure of which is totally incorporated herein by reference, particulate polymers, various metal oxides, and the like, preferably on the surface thereof.
Numerous toner and developer compositions without silicone oils, including those which are useful in electrostatic imaging systems with fusers without release agent management oil delivery systems, are known, reference for example British Patent 1,442,835, the disclosure of which is totally incorporated herein by reference. Most of these fuser subsystems employ hard roll fusers, that is Teflon, whereas the present invention can be selected with silicone soft roll fusers, including those which utilize a functionalized silicone oil for which a release agent management system is employed. Specifically, there is disclosed in the aforesaid British Patent No. 1,422,835 toner compositions comprised of a styrene homopolymer or copolymer resin and at least one polyalkylene compound selected from polyethylene and polypropylene. According to the disclosure of this patent, reference page 2, beginning at line 90, the starting polymer resin may be either a homopolymer of styrene, or a copolymer of styrene with other unsaturated monomers, specific examples of which are disclosed on page 3, beginning at line 1. Polyalkylene compounds selected for incorporation into the toner compositions disclosed in this patent include those of a low molecular weight, such as polyethylene, and polypropylenes of an average molecular weight of from about 2,000 to 6,000.
Additionally, there is disclosed in U.S. Pat. No. 4,460,672 a developer composition mixture comprised of electrostatic toner particles consisting of resin particles, pigment particles, a low molecular weight waxy material with a molecular weight of from about 500 to about 20,000, and further included in the composition from about 0.5 percent by weight to about 10 percent by weight of a charge enhancing additive selected from, for example, alkyl pyridinium halides, organic sulfonate compositions, and organic sulfate compositions. The disclosure of this patent is totally incorporated herein by reference.
Also, there is disclosed in U.S. Pat. No. 4,206,247 a developer composition comprised of a mixture of resins including a low molecular weight polyolefin and alkyl modified phenol resins. More specifically, it is indicated in this patent, reference column 4, line 6, that the invention is directed to a process which comprises the steps of developing an image with toner particles containing in certain proportions at least one resin selected from group B, wherein the resins of group A include a low molecular weight polyethylene, a low molecular weight polypropylene, and similar materials; and wherein the group B resins include natural resin modified maleic acid resins, and naturally modified pentaerythritol resins. As examples of group A resins there are mentioned polystyrene, styrene series copolymers, polyesters, epoxy resins and the like, reference the disclosure in column 5, line 47. The molecular weight of the polypropylene or polyethylene selected is from about 1,000 to about 10,000, and preferably from about 1,000 to about 5,000.
In addition, there are illustrated in U.S. Pat. No. 4,517,272 toner compositions prepared by admixing certain toner polymers and low surface energy liquids, see column 1, beginning at line 65, and column 2, continuing on to line 45. More specifically, it is indicated in column 2, beginning at line 9, that the toner polymer which can be a thermoplastic or thermosetting polymer with preferred components such as a pigment and charge control agent, and with the low surface energy liquid such as a silicone oil, is provided. Particularly useful toner polymers include styrene acrylic copolymers, polyesters, and similar materials, reference the disclosure in column 2, beginning at line 45. Examples of low surface energy liquids that may be selected are outlined in column 3, beginning at line 7. Although the present invention is directed to related subject matter, there is selected substantially different polymers enabling, for example, the release fluid to be controllably retained therein, and thus allowing a controlled release of small amounts of release fluid during the fusing. Uncontrolled leaching of release fluid is a disadvantage associated with the toners of the '272 patent. Moreover, it is believed that U.S. Pat. No. 4,517,272 does not teach how the bulk added silicone oil is retained such that the toner flow is acceptable, or agglomerates are prevented.
Also of interest is U.S. Pat. No. 3,485,787 which is directed to hydrogenated block copolymers containing oils therein, and more specifically elastomers of the general configuration A-B-A which are prepared by extending with mineral oil the aforementioned hydrogenated block copolymers, see the Abstract of the Disclosure, for example. In U.S. Pat. No. 4,552,914, there are illustrated hydrocarbon block copolymers with dispersed polysiloxanes, and more specifically wherein there is dispersed a polysiloxane through a thermoplastic elastomeric hydrocarbon resulting in compositions which can display a remarkably smooth surface, see column 4, beginning at line 36. Other prior art of primarily background interest include European Patent Publication 167,259; Japanese Patent Publications 54-48245, 58-136051, 59-33460, and 60-186869. In the '69 Japanese publication, there are disclosed pressure fixable microcapsule toners consisting of a shell core containing a silicone oil; while the '245 publication illustrates a magnetic toner containing a thermoplastic resin with a small amount of silicone oil. In the '051 Japanese publication, there is illustrated a method whereby a fixing device is used containing a heat roller coated without the use of oil and wherein the developer consists of small amounts of an adhesion inhibitor of which silicone resin is mentioned as an example; while the '460 Japanese publication illustrates a latent image developing toner used to coat a heat roll without requiring oil, and wherein the toner consists of a thermoplastic resin which does not significantly melt onto the heat roll. The '914 patent discloses a composition consisting of a hydrocarbon block copolymer and small amounts of silicone oil and mineral oil, the block copolymer containing a styrene ethylene butylene styrene macromolecule with silicone oil and mineral oil dispersed throughout the copolymer. Also, with further respect to the '787 patent, note column 4, lines 10 to 13, where there is illustrated elastomeric block copolymers which might include copolymers of styrene butadiene in combination with up to 50 percent of mineral oil. None of the aforementioned reference, however, are directed to toner compositions or processes of utilizing these compositions wherein there is selected the polyester polymers of the present invention having incorporated therein release fluids.
Developer compositions can be selected for use in developing electrostatic images, wherein the toner image is fixed to a permanent substrate such as paper by contacting the paper with a roller, the surface of which is formed from a material capable of preventing toner particles from sticking thereto. In this process, however, the surface of the fixing roll is brought into contact with the toner image in a hot melt state, thus a part of the toner image can adhere to and remain on the surface of the roll. This causes a part of the toner image to be transferred to the surface of a subsequent sheet on which the toner image is to be successively fixed, thereby causing the well known undesirable offset phenomena.
In order to substantially eliminate offsetting, and more specifically for the purpose of preventing adhesion of the toner particles to the surface of the fixing roller, there has been selected certain types of rollers, the surface of which may be covered with a thin film of an offset preventing liquid such as a silicone oil. These oils are highly effective, however, the apparatus within which they are incorporated is complicated and costly as indicated herein since, for example, a means for feeding the oil is required. Also, not only do the silicone oils emit an undesirable odor, but these oils deposit on the machine components causing toner particles to collect on, and adhere to the silicone oils, which is highly undesirable. An accumulation of toner particles on machine components is troublesome in that image quality is adversely effected and these components must be periodically cleaned and/or replaced, adding to the maintenance costs of the machine system involved.
With the present invention, while release additives are utilized such as silicone oils, these additives are incorporated into certain polymer compositions thereby avoiding the need for costly components to enable management of the silicone oils selected for many of the prior art methods. Accordingly, there is a need for toner and developer compositions which are useful in electrostatographic printing and imaging systems wherein release management components are avoided. More specifically, there is a need for toner compositions wherein the release fluid is incorporated into the polymer and released therefrom during the fusing of the image to the supporting substrate. There is also a need for toner compositions wherein the release fluid such as silicone oils, mineral oils, or hydrocarbon oils that are present in the polymer avoid agglomeration of the resulting toner particles. Moreover, there is a need for toner compositions, including colored toner compositions that permit images of high quality and excellent resolution with substantially no background deposition, and wherein costly release management components are avoided. There also remains a need for toner compositions which are particularly useful in electrostatographic imaging processes having incorporated therein polysiloxane or fluoropolymer elastomer fuser rolls. There is also a need for processes of imaging wherein the release fluid is incorporated into certain polymers thereby overcoming several of the disadvantages of the prior art including the avoidance of a costly release management system, and wherein toner agglomerates are not formed; rather, the toner particles are free flowing. Furthermore, there is a need for toner and developer compositions comprised of resin particles which have incorporated therein release additives which can be controllably delivered in small effective amounts to prevent offsetting while not depositing large amounts of oil on the final copy which would cause problems when subsequently attempting to write or type on this copy.